Range control system



June 16, 1936- F. s. WHEELER ,1

RANGE CONTROL SYSTEM Filed March 50, 1934 Z l l Lz [Ll/Q3,

WITNESSES: INVENTOR 5 F7050 5. whee/er,-

Patented June 16, 1936 UNITED STATES PATENT: OFFICE men comaor. sys'rau Pennsylvania Application March so, 1934, Serial No. 718,278

a Claims. (Cl. 21940) My invention relates to electric cooking appliances and particularly to temperature-control systems for electric ranges.

An object of my invention is to provide a relatively simple, inexpensive and easily installed and operated temperature-control system for an electric cooking appliance.

Another object of my invention is to provide a purely electric control system, particularly applicable to electric ranges, that shall permit of obtaining any one of a number of different temperature cycles in an electric cooking appliance.

Other objects of my invention will either be apparent from the following description of two embodiments of my invention or will be set forth in detail hereinafter.

In cooking certain types of foods such as roasts of meat, it is desirable that the meat be initially subjected to a temperature sufficiently high to sear the outer surface of the meat to seal the juices therein and to thereafter subject the meat to a lower maintained temperature to cook it to the desired degree. Heretofore in some of the priorart types of ranges, particularly the gas heated ranges, the operator was obliged to manually adjust the amount of fuel burned to obtain the peak of searing temperature and then reduce the temperature by proper manipulation of the control valve to provide a substantially constant lower value of temperature in a cooking chamber.

My invention is especially applicable to electrically heated ranges and provides a control system therefor embodying a minimum number of parts, more particularly thermally-actuable circult controllers which individually control the energization of the heating element either directly of indirectly, the circuit controllers being actuated in predetermined sequence by a single thermally actuabie element, which may be a bimetal member. The two circuit controllers may be rendered effective or ineffective, at the will of an operator, in order that different temperature cycles may be obtained.

In theaccompanying single sheet of drawing,

. Figure 1 is a diagram of connections showing one form of appliance and system embodying my invention, 7

Fig. 2 is a view similar to Fig. 1 but showing a modification of the system shown therein,

50 Fig. 3 is a view in front elevatlon of one form of circuit controller which I may use, and

Fig. 41s a view in front elevation of another form of circuit controller usable in the system and appliance embodying my invention. 55 My invention is closely related to copending applications Serial Nos. 718,272, 718,273, 718,274, 718,275, 718,276, and 718,277, filed concurrently herewith by H. M. Biebel and assigned to Westinghouse Electric and Manufacturing Company.

Referring first to Fig. 1 of the drawing, 1 have 5 there illustrated a cooking appliance comprising a plurality of walls I I enclosing a cooking chamher i 3 and having either located therein or op atively associated therewith a heating element l5 which is of suflicient heating capacity to raise m the temperature of the cooking chamber and of any food which may be placed therein to the desired value to-eflect desired cooking operations thereon.

A supply circuit for the heating element ii in- A5 eludes two supply circuit conductors L1 and L: and a manually operable switch I! which may be located on the cooking appliance itself.

As it may at times be desirable or necessary to. utilize a time control for starting and stopping the cooking operation, I may provide a time-controlled switch l9, shown schematically only, and in order to render this time-controlled switch effective or ineffective, I provide a manually-actuable switch 2| connected in parallel-circuit therewith. 25

One end of the heating element I8 is connected by a suitable conductor to a continuation of conductor L: while the other end thereof is connected to two switches or circuit controllers 23 and 25 respectively. These two circuit controllers may 30 be of any one of a number of different types of switches possessing certain characteristics necessary for the proper operation of my system, which characteristics will be hereinafter set forth in detail. 35

Referring now to Fig. 3 of the drawing, I have there illustrated one form of circuit controller 23 having two opposed limiting positions and comprising a plate 27, preferably of electric-in sulating material although not necessarily so. and on which there is pivotally-mounted a toroidal form of mercury switch 29 which includes, in a manner well known in the art, a closed annular casing of glass or quartz having two flexible leads 3! and 33 sealed into one wall thereof and a quantity of mercury 85, so that in one position of the switch the mercury will engage the ends of the flexible leads Ii and 33 to complete an electric circuit therethrough. -The torus 2! is pivotally mounted on a stud or bolt 37 secured to the base 21, and a diametrically-extending clamping member 88 supports the torus II on the pivot pin 31. At one end of the clamp 3.. there is an extension ll projecting beyond the torus to be engaged by a movable actuating member to is on the clamping -mernber 35 to positively hold positions, the first being tlia the switch in either one of its two limiting posioperative position as by end pins 45a. When the controller 23 is ifiKthe position shown in Fig. 3 of the drawing, the circuit therethrough is closed,

while if it is turned in a clockwise direction until clamp 39 engages stop pin 41, the circuit therethrough is interrupted. A slot 44 is provided in" plate" 21 to permit of adjusting the position of the switch, to cause operation thereof at diflerent temperatures. Other equivalent means to permit of adjustment may, however, be provided. Referring-now to Fig. 4 of the drawing, I have thereshown a somewhat diiierent form of circuit breaker 25 which is also pivotally mounted on a suitable support here shown as a plate 49. An arm 5|, of substantially Y-shape, and having two leg portio'ns'52 and 53 is pivotally mounted on the plate 49 as by a pivot pin or stud 54. A mercury switch 55 which may be in the form of ashort glassor quartz tube 51 is partially filled with mercury 59 and has the ends oi two flexible lead's 6| and'63 sealed into the tube and in engagement with the mercury in one position of the switch. A clamp 65 holds the tube 51 on the arm 5| and I prefer to so locate the switch or circuit controller 55 on the arm 5| that the switchwill remain in either one of two limiting t when the arm 5| engages an upper stop pin 51, when the circuit thro'ughthe switch is closed, and the second being that position when the arm 5| engages a; lower stop pin 59 and the circuit through the switch is open. A slot III is provided to'enable an opera-- tor to vary the position or location of the switch and therefore of its operating temperature.

Referring now again to-Fig. 1 of the drawing, the two switches or circuit controllers and 25, of Fig. 3 and Fig. 4, respectively, are shown as mounted on a single plate instead of on separate base plates, although this construction is not essential.

Actuation of the two circ it controllers is effected by a suitable thermally actuable' element, here shown as a bimetal strip I8 having one end thereof fixedly mounted as by being secured against a lug I5 secured to plate 1|, the other end or element 13 being free to move in response to variations of cooking chamber temperature.

As has already been stated, one of. each 01' the two flexible leads of'the respective circuit controllers 23 and 25 are connected together and to one end of the heating element i5 and it may be noted that leads 35 and 63 are so connected. The other lead 3| of controller 23 is connected to one end of a-manually actuable switch 5"1', the other terminal of which is connected to the continuation of supply circuit conductor in. The other flexible lead 5| ,of controller 225 is connected-to one terminal of a manually operable switch 19, the other terminal of which is also conductor L1.

Referring now to Fig. 2 of the drawing, I have there illustrated a modified term of system embodying my invention including, however, the hereinbeiore described supply circuit conductors L1 and Lo, the main manually operable switch I'I, the time-controlled switch I8 and the manually operable switch 2| shunting the time controlled contacts. f

The cooking chamber I3 is defined by a plurality of walls II and a heating element I5 is tions where the clamping support 39 is in nlocated therein. Substantially the same types of circuitcontrollers as were hereinbefore described in connection with Fig. 1 of the drawing are shown, but the current-carrying capacity of the respective circuit controllers 8| and 85 can be much less for the reason that they control only the circuit of the actuating coil 85 of a contactor, including in addition to the coil 85 the usual movable armature core 81 and a contact bridging member 85 movable therewith and engaging fixed contact members 9| connected in circuit with heating element I5 to control the energization thereof.

While the circuit controllers 25 and 25 of-Fig'. 1 had a current-carrying capacity suillciently large to properly. carry and interrupt the current traversing the heating element l5, which current may be on the order of =20 to amperes, circuit controllers 8| and 85 will be called upon to interrupt a circuit traversed by less than one ampere. A manually-operable switch 58 is connected in series circuit with controller 8| and a similar manually-operable switch 95 is connected in series circuit with controller 83. The two circuit controllers'fland 83 may be suitably mounted on a plate 91 which is also available for supporting a thermally actuable element 55 of the same kind as was hereinbeiore described in connection with the system 0! Fig. 1.

Simultaneous adjustment of the operating temperatures of the two circuit controllers in one or the other direction may be eflected in any ture 0t suflicient value to properly sear the same and to thereafter subject it to a lower maintained and substantially constant value until the roast shall have been cooked to the desired degree. To this end, the operator closes. the inanually operable switches l7 and 7-5 (or 53 and 55) and then closes the main switch l1 and, i! no time control is desired, also switch 2|. flhis effects energization of theheating element l5, through circuits including the parallel-connected controllers 25 and 25, for example, which will cause an increase in the temperature. of the .cooking chamber and a corresponding movement-oi the tree end oi':the bimetal strip 15 (or llfliiand for illustrative purposes it is to be assumedlhiat the lrec ends of these. strips wills-move [in counter clockwise direction, I f

The design and adjustment of circuit controlless 25 tand 53) relatively to the thermolly actuable member is suchthaqthe movable end of memberfl) (or 5%) will engage the upper arm 52 at a certain temperature, which bosom stantially the: desired maintained The result of this operative engagement oi the thermal element and fork arm 52 is that conroller 25, for example, is turned in a clockwise direction and against stop pin 69, thereby interrupting the circuit through the controller, as previously explained. This will have no eiIect, however, upon the energlzation or heating elenent l5, since the energization thereof is conalnued through circuit controller 23, for example, which is connected in electric parallel-circuit with controller 25.

' At a certain higher temperature, the movable and of the bimetal strip engages the projection or extension ll of controller 23, for example, and moves the, controller or switch to its open position. 'I'his has the result of deenergizing heating element l5 and it is to be understood hat the cooperation of thermal element 13 .or 99) with circuit breaker 23 (or BI) is such as to interrupt the circuit at a predetermined peak or relatively high temperature which for urposes of illustration may be assumed to be m the order of 500 to 550 F. The maximum temperature in the cooking chamber will, of course, be substantially momentary only and will decrease shortly after the interruption of the circuit through theheating element l5. At a certain lower temperature, the movable end 01' bimetal element 13 (or 99) will engage fork arm 53 of controller 25, for example, and cause the controller to turn in a counter clockwise direction to reclose the circuit therethrough which will reenergize heating element l5. For purposes of illustration, this lower temperature value may be considered as being on the order of 300or 400 F. and will be such a temperature as will properly cook either a roast or any other kind of food which may have been placed in the cooking chamber i 3.

The clockwise movement of the free end of bimetal strip 13 resultingnrom a decreasing temperature in the cooking chamber l8 will, therefore, be stopped a certain time after the reenergization of heating element I5, because of the translation of electric energy into heat therein with consequent reheating oi the cooking chamber and of any food placed therein. The bimetal strip will, therefore, again move in a counter clockwise direction, will-shortly reengage fork arm 52 and again effect opening at the circuit through controller 25 and since controller 23, for example, remains in its open position since bimetal strip 13 does not again on gage it and, in fact, is not adapted to move controller 23 in a counter-clockwise direction, control or the energization oi heating element I5 is now effected solely by controller 25, for example. The thermal element will, therefore, cooperate with controller 25 to intermittently sequentially energize and deenergize the heating element l5 to thereby maintain a substantially constant average value of temperature in the cooking chamber l3. As has already been stated, the heating element l5 may be finally deenergized either by the time-controlled switch I! or by manual operation of either of switches II or 2|.

Let it be assumed that the operator desires to obtain a momentary peak temperature value with a gradual but continuous decrease in temperature oi the cooking chamber. To this end, manual switch 19 of Fig. 1 is moved to open position and switch TI is moved to closed position or is left in such position. Heating element II will then be energized through controller 23 and switch 11, and bimetal strip 1: will move counter-clockwise in the manner hereinbefore described, moving controller 25 to open position heating element l5, and since thereafter the bimetal. strip moves in a clockwise direction in accordance with the gradually decreasing temperature of the cooking chamber, no further reenergiration of the heating element IE will be eflected (switch I! remaining open) and the cooking operation of the food placed in the cooking chamber iscompleted by stored heat.

Let it be assumed that the operator desires to provide a substantially constant maintained lower temperature value in the cooking'chamber, he will then open switch TI and either close switch I9 or leave it in its closed position. In this case, the movable end of bimetal strip 13' will operate in the manner hereinbefore set forth and will engage fork arm 52 at substantially the maintained temperature value to open the circuit through the heating element IS. The temperature in the cooking chamber will thereafter drop (since the circuit through controller 23 is open at switch 11), the bimetal strip will move in a clockwise direction and at a certain lower temperature it will engage fork arm 53 to reclose the circuit breaker and reenergize heating element I5. This intermittent sequential energization and deenergization will be continued for as long as the circuit or system is energized and may be discontinued, when desired, in the manner hereinbefore set forth either by the time clock I! 0 one 01' the two switches l1 and 2|.

The same two additional cycles of operations as to the temperatures in the cooking chamber It may be obtained by the system shown in, Fig. 2 or the drawing, it being noted however that the circuit controllers do not directly control the energization of heating element l5 but indirectly only, through the contactor shown as constituting a part of the system. It will be apparent that whereas switches 11 and I9 and circuit controllers 2S and 25 must have current-carrying capacity comparable to that of heating element '5, this is not the case as regards switches 93 and i5 and circuit controllers 8| and 83. While the system shown in Fig. 2 adds a contactor, it at the same time reduces the current carrying capacity of the two series-connected circuit-controlling devices in each of the two parallel circuits.

While I have shown a particular form of thermally actuable element, I do not desire to be limited thereto as any suitable or desired form c1 such thermally actuable-element may be used. I wish to point out that the bimetal element or its equivalent is not subjected to any initial stress but that it is free to move in direct accordance with the variations in the temperature of the cooking chamber. While I have shown and described particular embodiments oi circuit controllers, I do not desire to be limited thereto, as

' eluded. Circuit controllers 23 and Bi are, on the contrary, single-cycle switches or controllers;

that is, they will be individually operatively actuated by the thermal element once only in any one cycle of operation, this actuation being from an initially closed-circuit position to an opencircuit position, the controller remaining in such open-circuit position thereafter imtil manually moved to its closed-circuit position.

The device and system embodying my invention thus provide a relatively simple, purely electrical temperature control means whereby an operator may-obtain, at difierent times, any one of a number of different temperature cycles in a Booking chamber or other cooking appliance. The appliance and system-is not limited in its application to electric cooking but may be utilized in other fields where such temperature cycles may be desirable and useful.

Various further modifications may be made in the device and system embodying my invention ,without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art or are set forth in the appended claims.

,1 claim as my invention:

1. In an electric cooking appliance including a cooking chamberand a heating element therefor, means for controlling the energization of the heating element to obtain a momentary peak temperature and then a lowef maintained ternperature in the cooking chamber, said means including a, pair of parallel-connected switches individually controlling the energization of the heating element and a single thermally-actuable element movable in response to variations in the chamber temperature operatively mechanically shifting the two switches in. predetermined sequence to first openone of said switches at sub- ,stantially the maintained temperature value and to then open the second switch at substantially the peak temperature value and thereafter to operatively mechanically shift the first switch to close and open the same to thereby intermittently sequentially energize and deenergize the heating element to maintain a substantially con itant average temperature in the cooking. cham- 2. In an electric cooking appliance including a cooking chamber and a heating element therefor, means for controlling the energization of the heating element to obtain a momentary peak temperature and then a lower maintained temperature in the cooking chamber, said means including a pair of parallel-connected switches each connected in series circuit with the heating element" to directly control the energization thereof, and-a thermally-actuable element movable in response to variations in chamber temperature and mechanically engaging the two switches in sequence to move them to open position to effect deenergization of the heating ele-.-

ment at the desired peak temperature and then to again move the first-moved switch to effect sequential intermittent energization and deenergization of the heating ,elementto maintain a substantially constant average temperature in the cooking chamber.

3. In an electric cooking appliance including a cooking chamber and a heating element therefor, means for controlling. the energization of the heating element to obtain any -one of a plurality of temperature cycles in the cooking chamber, said means including a thermally-actuable member movable in response to variations in the chamber temperature, two switches severally controlling the energization of the heating element, electric conductors connecting the switches in parallel with each other and means for rendering the respective switches effective and inef-' fective, whereby-when both switches are eflective they will be mechanically actuated in the same directionby the thermally-actuable member in sequence to open position to,.deenergize the heating element at a predetermined peak temperature and thereafter to intermittently sequentially energize and deene'rgize the heating element ,to maintain a lower and substantially constant average value of temperature in the cooking chamber, .;and if the first of said switches is ineffective the thermally-notifiable member cooperates with the second fsyitch to. effect deenergizatio'n of the. heating element at a predetermined peak temperature and if the second of said switches is ineffective the jthermallygactuable member cooperates with theilrst switch onlyto intermittently sequentially energize and (H ghergize the heating element to maintain a predetermined lower substantially constant average value of temperature, in the cooking chamber.

4. An appliance as set forth in claim '3 in which the means for rendering theswit'ches effective and ineffective includes manually operable switches in series circuits with the respective flrst-named switches. 1

,5. In an electric cooking appliance including aiccqking chamber and a heating element therefor, meansfor controlling the energization of the heating element to obtain any one of a plurality of different temperature cycles in the cookthe thermally-act'uable member cooperateswith the two first-named switches in predetermined sequence to effect deenergization of the heating element at a peak temperature and then to intermittently sequentially energize and deenergize the heating element at substantially a lower maintained temperature and if the manuallyactuable switch in series circuit with the maintained temperature switch is open, the thermally-actuable member eifects'deenergization of the heating element by cooperation with the peak temperature switch and if the manually-actuable switch in series with the peak temperatureswitch is open the thermally-actuable member cooperates with the' maintained-temperature switch to intermittently sequentially energize and deenergize the heating element.

. 6. In a cooking appliance including a cooking chamber and a heating element therefor, means for controlling the energization of the heating element to obtain a momentary peak temperature and then a lower maintained temperature in the cooking chamber, said means including two pivotally mounted circuit controllers, a bimetal member having one end freely movable in response to variations in. chamber temperature and adapted to engage the circuit controllers to actuate the same and electric conductors connecting the circuit controllers in parallel with each other and in series with the heating element, the bimetal member first operatively engaging the two circuit controllers in predetermined sequence to move them to open position to deenergize the heating element at a predetermined peak temperature and to intermittently sequentially move one of said circuit controllers to closed and then to open position to maintain a lower predetermined temperature in the cooking chamber.

7. An appliance as set forth in claim 6 which includes a means for rendering efiective and ineffective the respective circuit controllers at the will of an operator.

8. In an electric heating device including a heating chamber and a heating element therefor, means for controlling the energization oi the heating element to automatically obtain a momentary peak temperature and then a lower maintained temperature in the heating chamber, said means including a single-cycle circuit-control device and a plural-cycle circuit-control device electrically connected in parallel with each other and selectively controlling the energization of the heating element, and a single thermallyactuable member movable in response to variations in chamber temperature for efiecting the successive operation of the several circuit-control devices to thereby efi'ect energization of the heating element until a certain peak temperature is reached in the heating chamber, next deenergize the heating element until a certain lower temperature is reached and thereafter intermittently sequentially energize and deenergize the heating element to maintain an average lower temperature in the heating chamber, said circuit-controlling devices being pivotally mounted mercury switches.

FLOYD 8. WHEELER. 

